it would be very interesting/helpful to have a standard dashboard widget to show directly all 404 calls with the referers leading to this page.
So you see directly after login
the data is already there... see
Good point, we should clearly list all 404 pages and also link to Transitions report, to see which lead to these 404 pages (external sites? internal links?)
it's just becoming even more interesting because even "normal" users who do not like editing files can use this function now since e.g. the magento plugin by Adrian supports this logging with the new version (this night, v1.10 see http://www.magentocommerce.com/magento-connect/piwik-ecommerce-7191.html#tab:releasenotes)
And when piwik is used in parse-apache-logs mode, it should be able to scan for all types of server errors without the need to inject a tag at all in generated error pages